Dark Awakening is the S3 episode I remember most vividly from childhood. In fact, it's the only S3 episode I remember from childhood. It definitely affected me and stuck with me, seeing Optimus dying again, his scary appearance (mainly the facial damage), and seeing the mausoleum and seeing a reminder that my favourites were dead.

I had seen the movie so knew they had died, and that had really upset me. This was upsetting all over again, and obviously made some kind of impression on me, being that it's the only s3 episode I remember from childhood.